Charge compensation semiconductor devices

ABSTRACT

A field-effect semiconductor device includes a semiconductor body having a first surface and an edge, an active area, and a peripheral area between the active area and the edge, a source metallization on the first surface and a drain metallization. In the active area, first conductivity type drift portions alternate with second conductivity type compensation regions. The drift portions contact the drain metallization and have a first maximum doping concentration. The compensation regions are in Ohmic contact with the source metallization. The peripheral area includes a first edge termination region and a second semiconductor region in Ohmic contact with the drift portions having a second maximum doping of the first conductivity type which lower than the first maximum doping concentration by a factor of ten. The first edge termination region of the second conductivity type adjoins the second semiconductor region and is in Ohmic contact with the source metallization.

PRIORITY CLAIM

This application is a Continuation-In-Part (CIP) of U.S. patentapplication Ser. No. 13/945,226 filed on 18 Jul. 2013, the content ofsaid application incorporated herein by reference in its entirety.

TECHNICAL FIELD

Embodiments of the present invention relate to semiconductor deviceshaving a charge compensation structure, in particular to powersemiconductor field-effect transistors having a charge compensationstructure and an edge-termination structure.

BACKGROUND

Semiconductor transistors, in particular field-effect controlledswitching devices such as a Metal Oxide Semiconductor Field EffectTransistor (MOSFET) or an Insulated Gate Bipolar Transistor (IGBT), havebeen used for various applications including but not limited to use asswitches in power supplies and power converters, electric cars,air-conditioners, and even stereo systems. Particularly with regard topower devices capable of switching large currents and/or operating athigher voltages, low on-state resistance Ron, high breakdown voltagesU_(bd), high robustness and/or good softness are often desired.

To achieve low on-state resistance Ron and high breakdown voltagesU_(bd), compensation semiconductor devices were developed. Thecompensation principle is based on a mutual compensation of charges inn- and p-doped regions, which are often also referred to as n- andp-doped pillar regions, in the drift zone of a vertical MOSFET.

Typically, the charge compensation structure formed by p-type and n-typeregions is arranged below the actual MOSFET-structure, with its source,body regions and gate regions, and also below the associatedMOS-channels that are arranged next to one another in the semiconductorvolume of the semiconductor device or interleaved with one another insuch a way that, in the off-state, their charges can be mutuallydepleted and that, in the activated state or on-state, there results anuninterrupted, low-impedance conduction path from a source electrodenear the surface to a drain electrode arranged on the back side.

By virtue of the compensation of the p-type and n-type dopings, thedoping of the current-carrying region can be significantly increased inthe case of compensation components, which results in a significantreduction of the on-state resistance Ron despite the loss of acurrent-carrying area. The reduction of the on-state resistance Ron ofsuch semiconductor power devices is associated with a reduction of theheat generated by the current in the on-state, so that suchsemiconductor power devices with charge compensation structure remain“cool” compared with conventional semiconductor power devices.

Meanwhile, switching losses of power semiconductor devices have becomemore important. Depending on device operation, output charge Q_(OSS) (oroutput capacitance C_(OSS)) and switching losses E_(OSS), respectively,stored in the space charge region formed in the off-state and duringreverse bias, respectively, mainly determine the switching losses. Thestored charge Q_(OSS) of semiconductor devices with charge compensationstructures may be comparatively high. This may result in significantswitching losses E_(OSS) when significant parts of the stored chargeQ_(oss) are removed at high voltages across load terminals of the powersemiconductor device. In addition to enable blocking, the output chargeQ_(OSS) (at specific blocking voltage) has to be completely removed,which results in switching delays.

To achieve high breakdown voltages U_(bd), an edge-termination structuremay be used in a peripheral area surrounding the active area with activeMOSFET-cells. However, the peripheral area requires chip area and thusincreases costs. Further, the edge-termination structure maysubstantially contribute to the output charge Q_(OSS) and outputcapacitance C_(OSS), respectively, for example to more than 10% of thetotal output capacitance C_(OSS).

Accordingly, there is a need to improve semiconductor devices withcharge compensation structures.

SUMMARY

According to an embodiment of a field-effect semiconductor device, thefield-effect semiconductor device includes a semiconductor body having afirst surface. The semiconductor body includes an edge delimiting thesemiconductor body in a direction substantially parallel to the firstsurface, an active area, and a peripheral area arranged between theactive area and the edge. The field-effect semiconductor device furtherincludes a source metallization arranged on the first surface and adrain metallization. In the active area the semiconductor body furtherincludes a plurality of drift portions of a first conductivity typealternating with compensation regions of a second conductivity type. Thedrift portions have a first maximum doping concentration and are inOhmic contact with the drain metallization. The compensation regions arein Ohmic contact with the source metallization. In the peripheral areathe semiconductor body further includes a first edge termination region,and a second semiconductor region in Ohmic contact with the driftportions and having a second maximum doping concentration of dopants ofthe first conductivity type which is lower than the first maximum dopingconcentration of the drift portions by a factor of at least five. Thefirst edge termination region is of the second conductivity type, inOhmic contact with the source metallization and adjoins the secondsemiconductor region.

According to an embodiment of a field-effect semiconductor device, thefield-effect semiconductor device includes a semiconductor body having afirst surface. A source metallization is arranged on the first surface.The semiconductor body includes an active area and a peripheral areasurrounding the active area. In the active area the semiconductor bodyfurther includes a plurality of alternating n-type drift portions andp-type compensation regions. The drift portions have a first maximumdoping concentration. The compensation regions are in Ohmic contact withthe source metallization. The semiconductor body further includes anedge termination region and a second semiconductor region in Ohmiccontact with the drift portions, extending in the peripheral area to thefirst surface and having a second maximum doping concentration of n-typedopants lower than the first maximum doping concentration. The edgetermination region is in Ohmic contact with the source metallization andadjoins the second semiconductor region. A concentration of p-typedopants in the edge termination region varies in a vertical directionsubstantially orthogonal to the first surface.

According to an embodiment of a field-effect semiconductor device, thefield-effect semiconductor device includes a semiconductor body having afirst surface. The semiconductor body includes an edge delimiting thesemiconductor body in a direction substantially parallel to the firstsurface, an active area, and a peripheral area arranged between theactive area and the edge. The semiconductor device further includes asource metallization arranged on the first surface, and a drainmetallization. In a vertical cross-section substantially orthogonal tothe first surface, the semiconductor body further includes: a pluralityof alternating first n-type pillar regions and first p-type pillarregions arranged in the active area; at least one second p-type pillarregion arranged in the peripheral area; and at least one second n-typepillar region arranged between the at least one second p-type pillarregion and the first p-type pillar regions. The first n-type pillarregions are in Ohmic contact with the drain metallization. An integrateddopant concentration of the first n-type pillar regions substantiallymatches an integrated dopant concentration of the first p-type pillarregions. The first p-type pillar regions are in Ohmic contact with thesource metallization. The at least one second p-type pillar region is inOhmic contact with the source metallization and has an integrated dopantconcentration smaller than the integrated dopant concentration of thefirst p-type pillar regions divided by the number of first p-type pillarregions. The at least one second n-type pillar region has an integrateddopant concentration smaller than the integrated dopant concentration ofthe first n-type pillar regions divided by the number of the firstn-type pillar regions.

Those skilled in the art will recognize additional features andadvantages upon reading the following detailed description, and uponviewing the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the figures are not necessarily to scale, insteademphasis being placed upon illustrating the principles of the invention.Moreover, in the figures, like reference numerals designatecorresponding parts. In the drawings:

FIG. 1 illustrates a vertical cross-section through a semiconductor bodyof a semiconductor device according to an embodiment;

FIG. 2 illustrates a section of the vertical cross-section through thesemiconductor device illustrated in FIG. 1 according to an embodiment;

FIG. 3 illustrates a vertical cross-section through a semiconductor bodyof a semiconductor device according to an embodiment;

FIG. 4 illustrates a vertical cross-section through a semiconductor bodyof a semiconductor device according to an embodiment;

FIG. 5 illustrates a vertical cross-section through a semiconductor bodyof a semiconductor device according to an embodiment;

FIG. 6 illustrates a vertical cross-section through the semiconductorbody of a semiconductor device according to an embodiment; and

FIG. 7 illustrates a horizontal cross-section through the semiconductorbody of the semiconductor device illustrated in FIG. 6 according to anembodiment.

DETAILED DESCRIPTION

In the following Detailed Description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “leading,” “trailing,” etc., is used withreference to the orientation of the Figure(s) being described. Becausecomponents of embodiments can be positioned in a number of differentorientations, the directional terminology is used for purposes ofillustration and is in no way limiting. It is to be understood thatother embodiments may be utilized and structural or logical changes maybe made without departing from the scope of the present invention. Thefollowing detailed description, therefore, is not to be taken in alimiting sense, and the scope of the present invention is defined by theappended claims.

Reference will now be made in detail to various embodiments, one or moreexamples of which are illustrated in the figures. Each example isprovided by way of explanation, and is not meant as a limitation of theinvention. For example, features illustrated or described as part of oneembodiment can be used on or in conjunction with other embodiments toyield yet a further embodiment. It is intended that the presentinvention includes such modifications and variations. The examples aredescribed using specific language which should not be construed aslimiting the scope of the appending claims. The drawings are not scaledand are for illustrative purposes only. For clarity, the same elementsor manufacturing steps have been designated by the same references inthe different drawings if not stated otherwise.

The term “horizontal” as used in this specification intends to describean orientation substantially parallel to a first or main horizontalsurface of a semiconductor substrate or body. This can be for instancethe surface of a wafer or a die.

The term “vertical” as used in this specification intends to describe anorientation which is substantially arranged perpendicular to the firstsurface, i.e. parallel to the normal direction of the first surface ofthe semiconductor substrate or body. Likewise, the term “horizontal” asused in this specification intends to describe an orientation which issubstantially arranged parallel to the first surface.

In this specification, a second surface of a semiconductor substrate ofsemiconductor body is considered to be formed by the lower or backsidesurface while the first surface is considered to be formed by the upper,front or main surface of the semiconductor substrate. The terms “above”and “below” as used in this specification therefore describe a relativelocation of a structural feature to another structural feature withconsideration of this orientation.

In this specification, n-doped is referred to as first conductivity typewhile p-doped is referred to as second conductivity type. Alternatively,the semiconductor devices can be formed with opposite doping relationsso that the first conductivity type can be p-doped and the secondconductivity type can be n-doped. Furthermore, some Figures illustraterelative doping concentrations by indicating “−” or “+” next to thedoping type. For example, “n⁻” means a doping concentration which isless than the doping concentration of an “n”-doping region while an“n⁺”-doping region has a larger doping concentration than the “n”-dopingregion. However, indicating the relative doping concentration does notmean that doping regions of the same relative doping concentration haveto have the same absolute doping concentration unless otherwise stated.For example, two different n⁺-doping regions can have different absolutedoping concentrations. The same applies, for example, to an n⁺-dopingand a p⁺-doping region.

Specific embodiments described in this specification pertain to, withoutbeing limited thereto, to field-effect semiconductor devices, inparticular to field-effect compensation semiconductor devices andmanufacturing methods therefor. Within this specification the terms“semiconductor device” and “semiconductor component” are usedsynonymously. The field-effect semiconductor device is typically avertical semiconductor device such as a vertical MOSFET with a sourcemetallization and an insulated gate electrode arranged on the firstsurface and a drain metallization arranged on a second surface arrangedopposite to the first surface. Typically, the field-effect semiconductordevice is a power semiconductor device having an active area with aplurality of MOSFET-cells for carrying and/or controlling a loadcurrent. Furthermore, the power semiconductor device has typically aperipheral area with at least one edge-termination structure at leastpartially surrounding the active area when seen from above.

The term “power semiconductor device” as used in this specificationintends to describe a semiconductor device on a single chip with highvoltage and/or high current switching capabilities. In other words,power semiconductor devices are intended for high current, typically inthe Ampere range and/or voltages of more than about 10 V or even morethan about 100 V or 500 V. Within this specification the terms “powersemiconductor device” and “power semiconductor component” are usedsynonymously.

The term “edge-termination structure” as used in this specificationintends to describe a structure that provides a transition region inwhich the high electric fields around an active area of thesemiconductor device change gradually to the potential at or close tothe edge of the device and/or between a reference potential such asground and a high voltage e. g. at the edge and/or backside of thesemiconductor device. The edge-termination structure may, for example,lower the field intensity around a termination region of a rectifyingjunction by spreading the electric field lines across the terminationregion.

The term “field-effect” as used in this specification intends todescribe the electric-field mediated formation of a conductive “channel”of a first conductivity type and/or control of conductivity and/or shapeof the channel in a semiconductor region of a second conductivity type,typically a body region of the second conductivity type. Due to thefield-effect, a unipolar current path through the channel region isformed and/or controlled between a source region of the firstconductivity type and a drift region of the first conductivity type. Thedrift region may be in contact with a drain region. The drift region andthe drain region are in low Ohmic contact with a drain electrode (drainmetallization). The source region is in low Ohmic contact with a sourceelectrode (source metallization). In the context of the presentspecification, the term “in Ohmic contact” intends to describe thatthere is a low-ohmic ohmic current path between respective elements orportions of a semiconductor device when no voltages or only small probevoltages are applied to and/or across the semiconductor device. Withinthis specification the terms “in Ohmic contact”, “in resistive electriccontact”, “electrically coupled”, and “in resistive electric connection”are used synonymously.

In the context of the present specification, the term “MOS”(metal-oxide-semiconductor) should be understood as including the moregeneral term “MIS” (metal-insulator-semiconductor). For example, theterm MOSFET (metal-oxide-semiconductor field-effect transistor) shouldbe understood to include FETs having a gate insulator that is not anoxide, i.e. the term MOSFET is used in the more general term meaning ofIGFET (insulated-gate field-effect transistor) and MISFET(metal-insulator-semiconductor field-effect transistor), respectively.The term “metal” for the gate material of the MOSFET should beunderstood to include or comprise electrical conductive materials likee. g. metal, alloys, doped polycrystalline semiconductors and metalsemiconductor compounds like metal silicides.

In the context of the present specification, the term “gate electrode”intends to describe an electrode which is situated next to, andinsulated from the body region and configured to form and/or control achannel region through the body region.

In the context of the present specification, the term “field electrode”intends to describe an electrode which is arranged next to asemiconductor region, typically the drift region, partially insulatedfrom the semiconductor region, and configured to expand a depletedportion in the semiconductor region by charging to an appropriatevoltage, typically a negative voltage with regard to the surroundingsemiconductor region for an n-type semiconductor region.

In the context of the present specification, the term “mesa” or “mesaregion” intends to describe a semiconductor region between two adjacenttrenches extending into the semiconductor substrate or body in avertical cross-section.

The term “commutating” as used in this specification intends to describethe switching of the current of a semiconductor device from a conductingdirection in which a pn-load junction, for example the pn-junctionbetween the body region and the drift region of a MOSFET, is forwardlybiased to the opposite direction or blocking direction in which thepn-load junction is reversely biased. The term “hard commutating” asused in this specification intends to describe commutating with a speedof at least about 10⁹ V/s, more typically with a speed of at least about5*10⁹ V/s.

In the following, embodiments pertaining to semiconductor devices andmanufacturing methods for forming semiconductor devices are explainedmainly with reference to silicon (Si) semiconductor devices.Accordingly, a monocrystalline semiconductor region or layer istypically a monocrystalline Si-region or Si-layer. It should, however,be understood that the semiconductor body can be made of anysemiconductor material suitable for manufacturing a semiconductordevice. Examples of such materials include, without being limitedthereto, elementary semiconductor materials such as silicon (Si) orgermanium (Ge), group IV compound semiconductor materials such assilicon carbide (SiC) or silicon germanium (SiGe), binary, ternary orquaternary III-V semiconductor materials such as gallium nitride (GaN),gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide(InP), indium gallium phosphide (InGaPa), aluminum gallium nitride(AlGaN), aluminum indium nitride (AlInN), indium gallium nitride(InGaN), aluminum gallium indium nitride (AlGaInN) or indium galliumarsenide phosphide (InGaAsP), and binary or ternary II-VI semiconductormaterials such as cadmium telluride (CdTe) and mercury cadmium telluride(HgCdTe) to name few. The above mentioned semiconductor materials arealso referred to as homojunction semiconductor materials. When combiningtwo different semiconductor materials a heterojunction semiconductormaterial is formed. Examples of heterojunction semiconductor materialsinclude, without being limited thereto, aluminum gallium nitride(AlGaN)-aluminum gallium indium nitride (AlGaInN), indium galliumnitride (InGaN)-aluminum gallium indium nitride (AlGaInN), indiumgallium nitride (InGaN)-gallium nitride (GaN), aluminum gallium nitride(AlGaN)-gallium nitride (GaN), indium gallium nitride (InGaN)-aluminumgallium nitride (AlGaN), silicon-silicon carbide (Si_(x)C_(1-x)) andsilicon-SiGe heterojunction semiconductor materials. For powersemiconductor applications currently mainly Si, SiC, GaAs and GaNmaterials are used. If the semiconductor body comprises a high band gapmaterial such as SiC or GaN which has a high breakdown field strengthand high critical avalanche field strength, respectively, the doping ofthe respective semiconductor regions can be chosen higher which reducesthe on-state resistance Ron in the following also referred to ason-resistance Ron.

With reference to FIG. 1, a first embodiment of a semiconductor device100 is explained. FIG. 1 illustrates a vertical cross-section through asemiconductor body 40 of the semiconductor device 100. The semiconductorbody 40 extends between a first surface 101, facing a vertical directionen, and a second surface 102 arranged opposite to the first surface 101.In a horizontal direction that is substantially parallel to the firstsurface 101, the semiconductor body 40 is delimited by an edge 41, forexample a sawing edge. The semiconductor body has an active area 110 anda peripheral area 120 arranged between the active area and the edge 41.Typically, the peripheral area 120 surrounds the active area 110 whenseen from above.

A source metallization 10 is arranged on the first surface 101. A drainmetallization 11 is arranged on the second surface 102, i.e. opposite tothe source metallization 10. Furthermore, a gate electrode 12 istypically also arranged on the first surface 101 and insulated from thesource metallization 10 and the semiconductor body 40 by a dielectricregion 13. The gate electrode 12 is connected to a gate metallizationthat is not shown in FIG. 1. Accordingly, the semiconductor device 100may be operated as a three-terminal device.

The semiconductor body 40 typically includes a bulk mono-crystallinematerial 4 and at least one epitaxial layer 3, 2, 1 formed thereon.Using the epitaxial layer(s) 3, 2, 1 provides more freedom in tailoringthe background doping of the material since the doping concentration canbe adjusted during deposition of the epitaxial layer or layers.

In the exemplary embodiment illustrated in FIG. 1, the semiconductorbody 40 includes a highly doped n-type drain region 4 that extends tothe second surface 102 and is in Ohmic contact with the drainmetallization 11 and with an n-type field-stop region 3 that adjoins thedrain region 4 and has a lower maximum doping concentration than thedrain region 4. The drain region 4 and the optional field-stop region 3are typically arranged in the active area 110 and the peripheral area120 and may extend to the edge 41.

In the active area 110, a plurality of alternating n-type drift portions1 and p-type compensation regions 6 forming respective pn-junctions witheach other are arranged. The drift portions 1 have a first maximumdoping concentration, which is typically higher than the maximum dopingconcentration of the field-stop region 3. The drift portions 1 are inOhmic contact with the drain metallization 11 (in the exemplaryembodiment via the adjoining field-stop region 3 and the drain region4), and typically extend to the first surface 101. For sake of clarity,only three drift portions 1 and two compensation regions 6 areillustrated in FIG. 1.

An (mathematically) integrated dopant concentration of the driftportions 1 substantially matches an integrated dopant concentration ofthe compensation regions 6. Accordingly, the drift portions 1 and thecompensation regions 6 form a pn-compensation structure 1, 6. The meandopant concentration of the drift portions 1 and compensation regions 6,i.e., the mathematically integrated difference of the donorconcentration and the acceptor concentration per volume, is typicallylower than the maximum doping concentration of the field-stop region 3,more typically lower than the mean doping concentration of thefield-stop region 3. Even more typically, the mean dopant concentrationof the drift portions 1 and compensation regions 6 is below 10% or below5% of the maximum dopant concentration of the drift portions 1 and/orthe compensation regions 6. Even more typically, the mean dopantconcentration of the drift portions 1 and compensation regions 6 issubstantially zero.

In the exemplary embodiment, the p-type compensation regions 6 areformed as vertically orientated pillars. Alternatively, the p-typecompensation regions 6 are formed as substantially vertically orientatedstrip-type parallelepipeds, rectangles or ellipsoids. In the following,the n-type drift portions 1 and the p-type compensation regions 6 arealso referred to as n-type pillar regions 1 and p-type pillar regions 6.

Depending on the manufacturing of the pn-compensation structure 1, 6,the dopant concentration may vary in the drift portions 1 and/orcompensation regions 6. This is illustrated in FIG. 1 by the dashedellipses, which indicate that the concentration of p-type dopants ishigher in the center of the four exemplary bubble-shaped portions ofeach of the compensation regions 6. The compensation regions 6 are inOhmic contact with the source metallization 10.

This is explained in more detail with regard to FIG. 2 illustrating anenlarged upper section of the semiconductor device 100 illustrated inFIG. 1. The illustrated section of FIG. 2 typically corresponds to anupper part of one of a plurality of unit cells 111 in the active area110 of the semiconductor device 100.

In the exemplary embodiment, a p⁺-type body contact region 5 c and twon⁺-type source regions 15 are formed in a p-type body region 5. Further,an optional p⁺-type contact region 6 c extends between the body contactregion 5 c and the compensation region 6. The body contact region(s) 5 cand the contact region(s) 6 c are not shown in FIG. 1 and the followingFigures for sake of clarity.

A portion 13 a of the dielectric region 13 is arranged between the firstsurface 101 and each of the gate electrodes 12, and extends in ahorizontal direction from the drift portion 1 along the body region 5 atleast to the source region 15 so that an inversion channel, which isalso referred to herein as MOS-channel, may be formed by thefield-effect in a channel region of the body region 5 along theportion(s) 13 a forming a gate dielectric region. Accordingly, thesemiconductor device 100 may be operated as a MOSFET.

The remaining portion of the dielectric region 13 forms an interlayerdielectric between the source metallization 10 and gate electrode 12 andfirst surface 101, respectively.

In the exemplary embodiment, the source metallization 10 is electricallycontacted with the source regions 15 and the body contact region 5 c viaa shallow trench contact formed through the interlayer dielectric 13 andinto the semiconductor body 40. In other embodiments, the sourcemetallization 10 electrically contacts the source region 15 and the bodycontact region 5 c substantially at the first surface 101.

According to another embodiment, the gate electrode(s) 12 and gatedielectric(s) 13 a may be formed in a respective trench extending fromthe first surface 101 into the semiconductor body 40. In thisembodiment, the body region 5 and source regions 15 adjoin an upper partof the respective trench while the drift portions 1 adjoin a lower partof the respective trench. In this embodiment, the drift portions 1 maynot extend to the first surface 101 in the active area 110. Referringagain to FIG. 1, further embodiments are explained.

According to an embodiment, the doping concentrations of the p-typecompensation regions 6 and the drift portions 1 are chosen such that, inthe off-state, their charges can be mutually depleted and that, in theon-state, an uninterrupted, low-resistive conduction path is formed fromthe source metallization 10 to the drain metallization 11.

As illustrated in FIG. 1, the interlayer dielectric 13 typically alsocovers the semiconductor body 40 in the peripheral area 120. Theinterlayer dielectric 13 may substantially extend to the edge 41.

In the exemplary embodiment, the drift portion 1 that is closest to theedge 41 does not contribute or does not significantly contribute to theforward current of the MOSFET 100 and is therefore not attributed to theactive area 110. The active area 110 may be defined by the presence ofsource regions 15 and insulated gate electrodes 12.

According to an embodiment, the semiconductor body 40 further includes ap-type edge termination region 7 in Ohmic contact with the sourcemetallization 10 (for example via a horizontal extension portion of thebody region 5′) and a second semiconductor region 2, which is in Ohmiccontact with the drift portions 1, which extends in the peripheral area120 to the first surface 101, and which has a second maximum dopingconcentration of n-type dopants lower than the first maximum dopingconcentration of the drift portions 1 and typically lower than themaximum doping concentration of the field-stop region 3. The p-type edgetermination region 7 adjoins the second semiconductor region 2 and has aconcentration of p-type dopants which varies in a vertical direction.

The second maximum doping concentration of n-type dopants is typicallylower than the first maximum doping concentration by at least a factorof five, more typically by at least a factor of about ten, even moretypically by a factor of at least about 20, even more typically by afactor of at least about 50, for example by a factor of about 100. Thesecond semiconductor region 2 may be an n-type semiconductor regionforming a pn-junction with the edge termination region 7. The secondsemiconductor region 2 may also be a substantially intrinsicsemiconductor region.

Accordingly, the compensation MOSFET 100 is provided with anedge-termination that requires less chip area than, for example, anedge-termination without source regions and based on alternating n-typeand p-type pillar regions with lower pitch than used in the active area.

The second semiconductor region 2 and the edge termination region 7typically surround the active area 110 when seen from above.

Further, the second semiconductor region 2 may extend into the activearea 110. For example, the second semiconductor region 2 may, in theactive area 110, be arranged between the field-stop region 3 and thecompensation structure 1, 6.

Typically, the concentration of the p-type dopants is largest at or atleast close to the first surface 101. The vertical concentration profileof the p-type dopants may be chosen similar as for a VLD (Variation ofLateral Doping) edge-termination structure in horizontal direction.

In other embodiments, the concentration of p-type dopants is largest ina vertical depth in a range from about 20% to about 50% of the verticalextension of the edge termination region 7. For example, theconcentration of p-type dopants may be largest at about a third of thevertical extension of the edge termination region 7.

The edge termination region 7 typically extends from the first surface101 into the second semiconductor region 2 to a depth that correspondsto about at least 30% of the depth of the compensation regions 6, moretypically to about at least 50% of the depth of the compensation regions6. The edge termination region 7 may even extend deeper into thesemiconductor body 40 than the compensation regions 6.

The (mathematically) vertically integrated concentration of the p-typedopants of the edge termination region 7 is typically lower compared tothe compensation regions 6 and may be in a range from about 5×10¹¹ cm⁻²to about 5×10¹² cm⁻². The maximum horizontal extension of the edgetermination region 7 is typically in a range from about 2 μm to about 20μm and may differ in a vertical direction from the first surface 101. Inother embodiments, the maximum horizontal extension of the edgetermination region 7 may occur distant to the first surface 101.

Due to the edge termination region 7, the load of the unit cells of theactive area 110 next to the edge 41 in the off-state (blocking mode) maybe significantly reduced, since the edge termination region 7 is, atsufficient high integrated doping concentration, only depleted at higherblocking voltage. Accordingly, the reduction of the output capacitanceC_(OSS) is delayed and thus the switching softness improved.

Due to the vertically varying concentration of p-type dopants of theedge termination region 7, the maximum of the electric field in theoff-state typically occurs in the bulk of the semiconductor body 40 andnot at its first surface 101. Accordingly, the impact of surface chargesat or on the first surface on the blocking capability is reduced.

Further, high avalanche stability may be achieved due to the verticallyvarying concentration of p-type dopants of the edge termination region7.

Even further, the semiconductor device 100 may be provided with two oreven more edge termination regions 7 with a vertically varyingconcentration of p-type dopants. The vertical and/or horizontalextension of the at least two edge termination regions 7 may besubstantially identical or differ.

Furthermore, the edge termination region 7 and the compensationstructure 1, 6 may be formed in common manufacturing processes. Forexample, several alternating epitaxial depositions and maskedp-implantations followed by a common drive-in may be used to form thecompensation structure 1, 6. To manufacture the edge termination region7 in parallel, only additional openings of the used implantation masksin the peripheral area 120 are required. This is because the (relative)difference of the integrated doping concentration between thecompensation regions 6 and the edge termination region 7 may be set bythe areas of the openings in the implantation mask. In otherembodiments, the edge termination region 7 and the compensationstructure 1, 6 may be formed in common manufacturing processes byfilling differently wide and differently deep trenches with p-dopedsemiconductor material, e. g., using an epitaxial deposition ofsemiconductor material.

As illustrated in FIG. 1, the concentration of p-type dopants may, in avertical cross-section, be substantially mirror symmetrical with respectto a central vertical axis of the edge termination region 7, asindicated by the dashed lines in the edge termination region 7corresponding to equi-concentration lines.

FIG. 3 illustrates a vertical cross-section through a field-effectsemiconductor device 200. The semiconductor device 200 is similar to thesemiconductor device 100 explained above with regard to FIGS. 1 and 2.However, the concentration of p-type dopants of the edge terminationregion 7 of semiconductor device 200 is, in the vertical cross-section,not mirror-symmetrical. In the exemplary embodiment illustrated in FIG.3, the concentration of p-type dopants has, along at least onehorizontal line crossing the edge termination region 7 and in at leastone horizontal cross-section, respectively, a maximum value and asteeper gradient towards the active area 110 compared to the oppositedirection. Accordingly, the edge termination region 7 and thus theperipheral area 120 of semiconductor device 200 may have an even smallerhorizontal extension resulting in further reduced device costs. Thedashed-dotted line in FIG. 3 corresponds to the inner interface betweenthe edge termination region 7 and the second semiconductor region andthe body region 5, respectively, in FIG. 1.

Non-mirror-symmetric edge termination region 7 may be manufactured in asimilar manner as mirror-symmetric one, by using an implantation maskthat is suitably slotted in the peripheral area 120.

FIG. 4 illustrates a vertical cross-section through a field-effectsemiconductor device 300. The semiconductor device 300 is similar to thesemiconductor device 100 explained above with regard to FIGS. 1 and 2.However, the semiconductor body 40 of the semiconductor device 200further includes an n-type channel-stop region 8 adjoining the secondsemiconductor region 2 and having a maximum doping concentration that ishigher than the second maximum doping concentration of the secondsemiconductor region 2. Typically, the channel-stop region 8 extends tothe first surface 101 and is arranged between the edge 41 and the edgetermination region 7. The channel-stop region 8 may extend substantiallyto the edge 41. In other embodiments, the channel-stop region 8 mayextend in a vertical direction from the first surface 101 to thefield-stop region 3 or even to the drain region 4.

Due to the channel-stop region 8, the electric field in the off-statedoes not, or at least almost does not, extend to the edge 41.Accordingly, a low leakage current is ensured, as crystal defects whichmay be caused by sawing are shielded by the highly doped channel-stopregion 8.

FIG. 5 illustrates a vertical cross-section through a field-effectsemiconductor device 400. The semiconductor device 400 is similar to thesemiconductor device 300 explained above with regard to FIG. 4. However,two exemplary n-type floating semiconductor regions 9 are completelyembedded in the edge termination region 7 of semiconductor device 400.The one or more n-type floating semiconductor regions 9 are typicallyarranged within the edge termination region 7 such that a space chargeregion formed during the off-state reaches the respective pn-junctionformed with the edge termination region 7.

The doping concentration of the one or more n-type floatingsemiconductor regions 9 may be in a range from about 10¹⁵ cm⁻³ to about10¹⁷ cm⁻³. Accordingly, an avalanche multiplication may occur in thespace charge region at the pn-junctions within the edge terminationregion 7 already at a comparatively low blocking voltage. The resultinghole-current typically improves the softness during hard commutating.

FIG. 6 illustrates a vertical cross-section through a field-effectsemiconductor device 500. The active area 110 of the field-effectsemiconductor device 500 is similar to the active area of thesemiconductor device 100 explained above with regard to FIGS. 1 and 2and also includes a compensation structure formed by a plurality ofalternating first n-type pillar regions (drift portions) 1 and firstp-type pillar regions (compensation regions) 6. The first p-type pillarregions 6 are in Ohmic contact with the source metallization 10 and thefirst n-type pillar regions 1 are in Ohmic contact with the drainmetallization 11 arranged opposite. An integrated dopant concentrationof the first n-type pillar regions 1 substantially matches an integrateddopant concentration of the first p-type pillar regions 6. The dashedellipses within the first n-type pillar regions 1 and the first p-typepillar regions 6 indicate optional sub-regions having a higher n-typedopant concentration and a higher p-type dopant concentration,respectively.

However, the semiconductor body 40 of the semiconductor device 500further includes a second p-type pillar region 6′ in Ohmic contact withthe source metallization 10 and a second n-type pillar region 1′ that isarranged between and forms respective pn-junctions with the secondp-type pillar region 6′ and the outermost first p-type pillar regions 6.The dashed ellipses within the second n-type pillar regions 1′ and thesecond p-type pillar regions 6′ indicate optional sub-regions having ahigher n-type dopant concentration and a higher p-type dopantconcentration, respectively. The second p-type pillar region 6′ isarranged in the peripheral area 120 and has an integrated dopantconcentration smaller than the integrated dopant concentration of thefirst p-type pillar regions 6 divided by the number of the first p-typepillar regions 6. The second n-type pillar region 1′ has an integrateddopant concentration smaller than the integrated dopant concentration ofthe first n-type pillar regions 1 divided by the number of the firstn-type pillar regions 1. The second n-type pillar region 1′ may or maynot contribute to the forward current. Accordingly, the gate electrode12 arranged above the second n-type pillar region 1′ is only optional.Depending on its contribution to the forward current, the second n-typepillar region 1′ is attributed to the active area 110 and peripheralarea 120, respectively. The body region 5′ arranged between the secondp-type pillar region 6′ and the source metallization 10 does not includea source region or includes a source region which is surrounded by asufficient amount of p-dopants to inhibit the forming of an electronchannel and is therefore arranged in the peripheral area 120. The secondn-type pillar region 1′ and the second p-type pillar region 6′ may alsobe considered as forming a transitional area or zone between the activearea 110 and peripheral area 120.

Due to the reduced doping of the second n-type pillar region 1′ and thesecond p-type pillar region 6′ compared to the compensation structure 1,6, the potential drop across the second n-type pillar region 1′ and thesecond p-type pillar region 6′ is also lower during the off-state(blocking mode). Accordingly, any avalanche breakdown is expected tooccur in the active area 110 only. Due to the larger area of the activearea 110 compared to the peripheral area 120, the semiconductor device500 tolerates higher avalanche currents and avalanche energies,respectively, without damaging.

For applications with rare or none avalanche events, such as in resonantcircuits, the transitional area may be omitted to further reduce thearea of the peripheral area 120.

In the peripheral area 120, the semiconductor body 40 includes: ann-type second semiconductor region 2 that adjoins the second p-typepillar region 6′ and has a second maximum doping concentration lowerthan a first maximum doping concentration of the second n-type pillarregion 1′; a p-type first edge termination region 17 adjoining thesecond semiconductor region 2; and an n-type second edge terminationregion 18. The second maximum doping concentration of n-type dopants istypically lower than a first maximum doping concentration of the firstn-type pillar regions 1 by at least a factor of five, more typically byat least a factor of ten, for example, by a factor of about 50 or ofabout 100. Due to the low concentration of n-type dopants in the secondsemiconductor region 2, the contribution of the second semiconductorregion 2 to the total output charge Q_(OSS) is very low.

The n-type second edge termination region 18 has a fourth maximum dopingconcentration higher than the second maximum doping concentration,adjoins the first edge termination region 17, and is at least partlyarranged between the first edge termination region 17 and the firstsurface 101. Typically, a vertically integrated dopant concentration ofthe n-type second edge termination region 18 matches or is lower than avertically integrated dopant concentration of the p-type second edgetermination region 17.

The output charge Q_(OSS) of the peripheral area 120 is mainlydetermined by the n-type second edge termination region 18, the p-typefirst edge termination region 17 and the second p-type pillar region 6′but significantly lower than for edge-termination structures based oncompensated inactive alternating n-type and p-type pillar regionsextending into the peripheral area 120.

In the exemplary embodiment illustrated in FIG. 6, the p-type first edgetermination region 17 is in Ohmic contact with the source metallization10.

In another embodiment, the first edge termination region 17 is afloating semiconductor region. In this embodiment, the semiconductordevice 500 is typically designed such that a space charge regionexpanding from the pn-junction formed between the n-type secondsemiconductor region 2 and the second p-type pillar region 6′ reachesthe first edge termination region 17 and the pn-junction formed betweenthe n-type second semiconductor region 2 and the first edge terminationregion 17, respectively, already at a low reverse voltage of for exampleat most 5% or 10% of the rated blocking voltage.

The first edge termination region 17 typically acts as a JTE (JunctionTermination Extension)-region and is in the following also referred toas JTE-region 17. The p-type dopant concentration in the JTE region 17may be constant or decreasing continuously or in discrete steps withdecreasing distance from the edge 41. The latter is indicated in FIG. 6by the two portions 17 a, 17 b of the JTE-region 17. Correspondingly,the n-type dopant concentration in the n-type second edge terminationregion 18 may be constant or decreasing continuously or in discretesteps with decreasing distance from the edge 41. The latter is indicatedin FIG. 6 by the two portions 18 a, 18 b of the n-type second edgetermination region 18. The n-type second edge termination region 18stabilizes the edge-termination structure against surface charges on thefirst surface 101 and reduces the injection of holes into the dielectricregion 13.

Further and similar as explained above with regard to FIG. 4, an n-typechannel-stop region 8 having a third maximum doping concentration higherthan the second maximum doping concentration adjoins the secondsemiconductor region 2 and may extend to the edge 41 for reducing theleakage current. In other embodiments, the channel-stop region 8 mayextend in a vertical direction from the first surface 101 to thefield-stop region 3 or even to the drain region 4.

In the exemplary embodiment illustrated in FIG. 6, the semiconductordevice 500 further includes a field plate 12 a in Ohmic contact with thegate electrodes 12 and a gate metallization (not shown in FIG. 6),respectively, and a field plate 11 a in Ohmic contact with the drainmetallization 12. Accordingly, the electric field distribution in theoff-state may be further smoothed and/or the sensitivity of thesemiconductor device 500 with respect to mobile charges in thedielectric region 13 be further reduced.

The field plate 11 a is typically arranged close to the edge 41. Thefield plate 11 a is typically arranged between the field plate 12 a andthe source metallization 10.

The field plate 11 a and/or the field plate 12 a may be stepped asillustrated in FIG. 6, i.e., the vertical (minimum) distance of thefield plates 11 a and/or 12 a from the first surface 101 may changesubstantially stepwise in a horizontal direction. The number of stepsmay also be higher or lower compared to the exemplary embodimentillustrated in FIG. 6. In other embodiments, only one or even none ofthe field plate 11 a, 12 a is arranged on the first surface 101.

FIG. 7 illustrates an edge section of a horizontal cross-section throughthe semiconductor body 40 of the semiconductor device 500 illustrated inFIG. 6 beneath the JTE-region 17. Typically, the active area 110 issurrounded by a contiguous channel-stop region 8 when viewed from above.The boundary between the active area 110 and the peripheral area 120 isindicated by dashed lines in FIG. 7. For sake of clarity, only fourfirst p-type pillar regions 6 of active area 110 are illustrated in FIG.7. FIG. 6 typically corresponds to a cross-section along line 501defining an x-direction. As illustrated in FIG. 7, the first p-typepillar regions 6 and the first n-type pillar regions 1 typically adjointhe second p-type pillar regions 6′. In this embodiment, the active area110 is typically surrounded by a contiguous second p-type pillar region6′ when viewed from above.

The minimum distance d_(y) in y-direction (elongation direction of theregions 1, 1′, 6 in horizontal cross-sections) between the secondsemiconductor region 2 and the first n-type pillar regions 1 and thefirst p-type pillar regions 6, respectively, may be equal to but alsosmaller than the maximum distance in x-direction d_(x) of about 20 μm,between the second n-type pillar region 1′ and the second semiconductorregion 2. For example, the ratio d_(y)/d_(x) may be smaller than about0.8 or even 0.5. Typically, the minimum distance d_(y) in y-directionbetween the second semiconductor region 2 and the first n-type pillarregions 1 substantially equals the minimum distance in y-directionbetween the second semiconductor region 2 and the second n-type pillarregions 1′.

In another embodiment, the first and second n-type pillar regions 1, 1′extend in the y-direction at least to the second semiconductor region 2.This is illustrated in FIG. 7 by the dashed-dotted curves. In thisembodiment, the first p-type pillar regions 6 typically adjoin thesecond semiconductor region 2 and the second p-type pillar region 6′does not adjoin the first p-type pillar regions 6. Note that the drop ofthe electric potential during the blocking-mode of the semiconductordevice 500 is typically different for the x-direction and they-direction, due to the geometry and the arrangement of the pillarregions 1, 6 in the active area 110. The peripheral area 120 may beformed accordingly.

Furthermore, the first and second n-type pillar regions 1, 1′ may have areduced and/or decreasing extension in x-direction close to the secondsemiconductor region 2.

Further, the concentration of dopants is typically reduced iny-direction close to and towards the second semiconductor region 2.

Referring again to FIG. 6, further embodiments are explained. Typically,the integrated absolute dopant concentration of the second p-type pillarregion 6′ is smaller than the integrated absolute dopant concentrationof the second n-type pillar region 1′, which is smaller than theintegrated absolute dopant concentration of the first p-type pillarregions 6 substantially matching the integrated absolute dopantconcentration of the first n-type pillar region 1.

Typically, the integrated concentration of p-type dopants in the secondp-type pillar region 6′ is smaller than the integrated concentration ofn-type dopants in the second n-type pillar region 1′ by a factor ofabout 2.

The integrated dopant concentration of the second n-type pillar region1′ is typically in a range from about 50% to about 99% of the integrateddopant concentration of the first n-type pillar region 1.

The integrated dopant concentration of the second p-type pillar region6′ is typically in a range from about 25% to about 60% of the integrateddopant concentration of the first p-type pillar region 6.

In further embodiments, more than one pair of second pillar regions 1′,6′ is used, typically with decreasing integrated dopant concentrationtowards the edge. In further embodiments, the integrated dopantconcentrations of the second p-type pillar regions 6′ and of the secondn-type pillar regions 1′ decrease with an increasing distance from theactive area 110 in a lateral direction.

According to numerical simulations of the semiconductor device 500illustrated in FIG. 6, the corrugation of the electric potential in thesecond p-type pillar region 6′ is reduced compared to the first pillarregions 1, 6. Accordingly, avalanche multiplication will occur only inthe active area 110 as affirmed by analyzing the correspondinggeneration of charge carriers. According to the simulations, thehorizontal extension of the peripheral area 120 of the semiconductordevice 500 could even further be reduced. This would result in an evenlower product of R_(on) times Q_(oss).

The field-effect semiconductor device 500 may also be described as asemiconductor device 500 having a semiconductor body 40 including afirst surface 101, an edge 41 delimiting the semiconductor body 40 in adirection substantially parallel to the first surface 101, an activearea 110, and a peripheral area 120 arranged between the active area 110and the edge 41. A source metallization 10 is arranged on the firstsurface, and a drain metallization 11 is arranged opposite to the sourcemetallization 10. In the active area 110, the semiconductor body 40further includes a plurality of alternating n-type drift portions 1 andp-type compensation regions 6, the drift portions 1 having a firstmaximum doping concentration and being in Ohmic contact with the drainmetallization 11. The compensation regions 6 are in Ohmic contact withthe source metallization 10. The semiconductor body 40 further includesa second semiconductor region 2 in Ohmic contact with the drainmetallization 11 and having a second maximum doping concentration ofdopants of the first conductivity type that is lower than the firstmaximum doping concentration. In the peripheral area 120, thesemiconductor body 40 further includes: a p-type first edge terminationregion 17 adjoining the second semiconductor region 2, and an n-typesecond edge termination region 18 having a fourth maximum dopingconcentration higher than the second maximum doping concentration,adjoining the first edge termination region 17, and being arranged atleast partly between the first edge termination region 17 and the firstsurface 101.

The field-effect semiconductor devices explained above with regard tothe above Figures have in common that they include a semiconductor body40 having a first surface 101, an edge 41 delimiting the semiconductorbody 40 in a direction substantially parallel to the first surface 101,an active area 110, and a peripheral area 120 arranged between theactive area 110 and the edge 41. A source metallization 10 is arrangedon the first surface 101 and a drain metallization 11 is arrangedopposite to the source metallization 10. In the active area 110, thesemiconductor body 40 further includes: a plurality of drift portions 1of a first conductivity type alternating with compensation regions 6 ofa second conductivity type. The drift portions 1 have a first maximumdoping concentration and are in Ohmic contact with the drainmetallization 11. The compensation regions 6 are in Ohmic contact withthe source metallization 10. In the peripheral area 120 thesemiconductor body 40 further includes: a second semiconductor region 2in Ohmic contact with the drift portions 1 and having a second maximumdoping concentration of dopants of the first conductivity type which islower than the first maximum doping concentration of the drift portions1 by a factor of at least five, more typically by a factor of at leastten; and a first edge termination region 7, 17 of the secondconductivity type in Ohmic contact with the source metallization 10 andadjoining the second semiconductor region 2.

Typically, an integrated dopant concentration of the drift portions 1 inthe active area 110 substantially matches an integrated dopantconcentration of the compensation regions 6 in the active area 110.

The first edge termination region 7, 17 and the second semiconductorregion 2 may form a pn-junction.

Typically, the second maximum doping concentration is lower than thefirst maximum doping concentration by at least a factor of fifty.

According to an embodiment, the semiconductor body 40 further includes,in the peripheral area 120, a channel-stop region 8 of the firstconductivity type, which has a third maximum doping concentration higherthan the second maximum doping concentration, is in Ohmic contact withthe second semiconductor region 2, and is arranged between the edge 41and at least one of the first edge termination region 7, 17 and thesecond semiconductor region 2.

According to an embodiment, the semiconductor body 40 further includes asecond edge termination region 18 of the first conductivity type havinga fourth maximum doping concentration higher than the second maximumdoping concentration in the peripheral area 120. The second edgetermination region 18 is in Ohmic contact with the drain metallization11, adjoins the first edge termination region 17, and is arrangedbetween the first edge termination region 17 and the first surface.

Typically, the second edge termination region 18 includes a firstportion 18 a and a second portion 18 b that has a lower maximum dopingconcentration than the first portion 18 a and is arranged between thefirst portion 18 a and the edge 41.

Likewise, the first edge termination region 17 typically includes afirst portion 17 a and a second portion 17 b that has a lower integrateddoping concentration than the first portion 17 a and is arranged betweenthe first portion 17 a and the edge 41.

According to an embodiment, a concentration of dopants of the secondconductivity type is, in a vertical direction, varied in the first edgetermination region 7 such that the concentration is largest at leastclose to the first surface 101.

At least one floating semiconductor region 9 of the first conductivitytype may be completely embedded in the first edge termination region 7.

According to an embodiment, the semiconductor body 40 includes, in theperipheral area 120, a further compensation region 6′ of the secondconductivity type in Ohmic contact with the source metallization 10,wherein the semiconductor body 40 further includes a semiconductorportion 1′ forming a pn-junction with the further compensation regions6′ and a further pn-junction one of the compensation regions 6, whereinan integrated dopant concentration of the semiconductor portion 1′ issmaller than the integrated dopant concentration of the drift portions 1divided by the number of the drift portions 1, and wherein an integrateddopant concentration of the further compensation region 6′ is smallerthan the integrated dopant concentration of the semiconductor portion 1′and/or smaller than the integrated dopant concentration of thecompensation regions 6 divided by the number of the compensationregions.

According to an embodiment, the field-effect semiconductor furtherincludes an dielectric region 13 arranged on the first surface 101, afield plate 11 a arranged on the first surface 101 and in ohmic contactwith the drain metallization 11, and/or a field plate 12 a arranged onthe first surface 101 and in ohmic contact with the gate metallizationor the source metallization 10 arranged on the first surface 101.

Although various exemplary embodiments of the invention have beendisclosed, it will be apparent to those skilled in the art that variouschanges and modifications can be made which will achieve some of theadvantages of the invention without departing from the spirit and scopeof the invention. It will be obvious to those reasonably skilled in theart that other components performing the same functions may be suitablysubstituted. It should be mentioned that features explained withreference to a specific figure may be combined with features of otherfigures, even in those cases in which this has not explicitly beenmentioned. Such modifications to the inventive concept are intended tobe covered by the appended claims.

Spatially relative terms such as “under,” “below,” “lower,” “over,”“upper” and the like are used for ease of description to explain thepositioning of one element relative to a second element. These terms areintended to encompass different orientations of the device in additionto different orientations than those depicted in the figures. Further,terms such as “first,” “second,” and the like, are also used to describevarious elements, regions, sections, etc. and are also not intended tobe limiting. Like terms refer to like elements throughout thedescription.

As used herein, the terms “having,” “containing,” “including,”“comprising” and the like are open ended terms that indicate thepresence of stated elements or features, but do not preclude additionalelements or features. The articles “a,” “an” and “the” are intended toinclude the plural as well as the singular, unless the context clearlyindicates otherwise.

With the above range of variations and applications in mind, it shouldbe understood that the present invention is not limited by the foregoingdescription, nor is it limited by the accompanying drawings. Instead,the present invention is limited only by the following claims and theirlegal equivalents.

What is claimed is:
 1. A field-effect semiconductor device, comprising:a semiconductor body comprising a first surface, an edge delimiting thesemiconductor body in a direction substantially parallel to the firstsurface, an active area, and a peripheral area arranged between theactive area and the edge; a source metallization arranged on the firstsurface; and a drain metallization, in the active area the semiconductorbody further comprising: a plurality of drift portions of a firstconductivity type alternating with compensation regions of a secondconductivity type, the drift portions comprising a first maximum dopingconcentration and being in Ohmic contact with the drain metallization,the compensation regions being in Ohmic contact with the sourcemetallization, in the peripheral area the semiconductor body furthercomprising: a second semiconductor region in Ohmic contact with thedrift portions and comprising a second maximum doping concentration ofdopants of the first conductivity type, the second maximum dopingconcentration being lower than the first maximum doping concentration ofthe drift portions by a factor of at least five; a first edgetermination region of the second conductivity type in Ohmic contact withthe source metallization and adjoining the second semiconductor region,and a second edge termination region of the first conductivity typecomprising a fourth maximum doping concentration higher than the secondmaximum doping concentration, the second edge termination region beingin Ohmic contact with the drain metallization, adjoining the first edgetermination region, and being arranged between the first edgetermination region and the first surface.
 2. The field-effectsemiconductor device of claim 1, wherein the second maximum dopingconcentration is lower than the first maximum doping concentration by atleast a factor of ten.
 3. The field-effect semiconductor device of claim1, wherein the first edge termination region and the secondsemiconductor region form a pn-junction.
 4. The field-effectsemiconductor device of claim 1, wherein the semiconductor body furthercomprises, in the peripheral area, a channel-stop region of the firstconductivity type comprising a third maximum doping concentration higherthan the second maximum doping concentration, being in Ohmic contactwith the second semiconductor region, and being arranged between theedge and at least one of the first edge termination region and thesecond semiconductor region.
 5. The field-effect semiconductor device ofclaim 1, wherein the second edge termination region comprises a firstportion and a second portion that has a higher maximum dopingconcentration than the first portion and is arranged between the firstportion and the edge.
 6. The field-effect semiconductor device of claim1, wherein the first edge termination region comprises a first portionand a second portion that has a lower integrated doping concentrationthan the first portion and is arranged between the first portion and theedge.
 7. The field-effect semiconductor device of claim 1, wherein aconcentration of dopants of the second conductivity type is, in avertical direction substantially orthogonal to the first surface, variedin the first edge termination region, and/or wherein the concentrationis largest at least close to the first surface.
 8. The field-effectsemiconductor device of claim 1, wherein the semiconductor body furthercomprises at least one floating semiconductor region of the firstconductivity type, which floating semiconductor region is completelyembedded in the first edge termination region.
 9. The field-effectsemiconductor device of claim 1, wherein an integrated dopantconcentration of the drift portions in the active area substantiallymatches an integrated dopant concentration of the compensation regionsin the active area.
 10. The field-effect semiconductor device of claim1, wherein the semiconductor body comprises in the peripheral area afurther compensation region of the second conductivity type in Ohmiccontact with the source metallization, wherein the semiconductor bodycomprises a semiconductor portion forming a pn-junction with the furthercompensation region and one of the compensation regions, wherein anintegrated dopant concentration of the semiconductor portion is smallerthan the integrated dopant concentration of the drift portions dividedby a number of the drift portions, and wherein an integrated dopantconcentration of the further compensation region is smaller than theintegrated dopant concentration of the semiconductor portion and/orsmaller than the integrated dopant concentration of the compensationregions divided by a number of the compensation regions.
 11. Thefield-effect semiconductor device of claim 1, further comprising atleast one of: an dielectric region arranged on the first surface; afield plate arranged on the first surface and in ohmic contact with thedrain metallization; and a field plate arranged on the first surface andin ohmic contact with the source metallization or with a gatemetallization arranged on the first surface.
 12. A field-effectsemiconductor device, comprising: a semiconductor body comprising afirst surface, an active area, and a peripheral area surrounding theactive area; and a source metallization arranged on the first surface,in the active area the semiconductor body further comprising: aplurality of alternating n-type drift portions and p-type compensationregions, the drift portions comprising a first maximum dopingconcentration, the compensation regions being in Ohmic contact with thesource metallization, the semiconductor body further comprising: asecond semiconductor region in Ohmic contact with the drift portions,extending in the peripheral area to the first surface and comprising asecond maximum doping concentration of dopants of the first conductivitytype, the second maximum doping concentration being lower than the firstmaximum doping concentration; and an edge termination region in Ohmiccontact with the source metallization, adjoining the secondsemiconductor region, and having a concentration of p-type dopants whichvaries in a vertical direction substantially orthogonal to the firstsurface.
 13. The field-effect semiconductor device of claim 12, whereinthe concentration of p-type dopants is largest at least close to thefirst surface.
 14. The field-effect semiconductor device of claim 12,wherein the concentration of p-type dopants is, in a verticalcross-section substantially orthogonal to the first surface,substantially mirror-symmetrical with respect to a vertical axis. 15.The field-effect semiconductor device of claim 12, wherein thesemiconductor body comprises at least one of: an edge delimiting thesemiconductor body in a direction substantially parallel to the firstsurface; at least one n-type floating semiconductor region which isembedded in the edge termination region; and an n-type channel-stopregion comprising a third maximum doping concentration higher than thesecond maximum doping concentration, in Ohmic contact with the secondsemiconductor region, and being arranged between the edge and at leastone of the edge termination region and the second semiconductor region.16. A field-effect semiconductor device, comprising: a semiconductorbody comprising a first surface, an edge delimiting the semiconductorbody in a direction substantially parallel to the first surface, anactive area, and a peripheral area arranged between the active area andthe edge; a source metallization arranged on the first surface, and adrain metallization, in a vertical cross-section substantiallyorthogonal to the first surface the semiconductor body furthercomprising: a plurality of alternating first n-type pillar regions andfirst p-type pillar regions arranged in the active area, the firstn-type pillar regions being in Ohmic contact with the drainmetallization, the first p-type pillar regions being in Ohmic contactwith the source metallization, and an integrated dopant concentration ofthe first n-type pillar regions substantially matching an integrateddopant concentration of the first p-type pillar regions; at least onesecond p-type pillar region in Ohmic contact with the sourcemetallization, arranged in the peripheral area and having an integrateddopant concentration smaller than the integrated dopant concentration ofthe first p-type pillar regions divided by a number of the first p-typepillar regions; and at least one second n-type pillar region arrangedbetween the at least one second p-type pillar region and the firstp-type pillar regions, directly contacting the first surface, and havingan integrated dopant concentration smaller than the integrated dopantconcentration of the first n-type pillar regions divided by a number ofthe first n-type pillar regions.
 17. The field-effect semiconductordevice of claim 16, wherein the integrated dopant concentration of theat least one second p-type pillar region is smaller than the integrateddopant concentration of the at least one second n-type pillar region.18. The field-effect semiconductor device of claim 16, wherein theintegrated dopant concentration of the at least one second n-type pillarregion is in a range from about 50% to about 99% of the integrateddopant concentration of the first n-type pillar regions divided by thenumber of the first n-type pillar regions.
 19. The field-effectsemiconductor device of claim 16, further comprising at least one of: anedge delimiting the semiconductor body in a direction substantiallyparallel to the first surface; an n-type second semiconductor regionadjoining the at least one second p-type pillar region in the peripheralarea and comprising a second maximum doping concentration lower than afirst maximum doping concentration of the at least one second n-typepillar region; a p-type first edge termination region adjoining thesecond semiconductor region; an n-type second edge termination regioncomprising a fourth maximum doping concentration higher than the secondmaximum doping concentration, adjoining the first edge terminationregion, and being arranged between the first edge termination region andthe first surface; and an n-type channel-stop region comprising a thirdmaximum doping concentration higher than the second maximum dopingconcentration, being in Ohmic contact with the second semiconductorregion and being arranged between the edge and at least one of the firstedge termination region and the second semiconductor region.
 20. Afield-effect semiconductor device, comprising: a semiconductor bodycomprising a first surface, an edge delimiting the semiconductor body ina direction substantially parallel to the first surface, an active area,and a peripheral area arranged between the active area and the edge; asource metallization arranged on the first surface; and a drainmetallization, in the active area the semiconductor body furthercomprising: a plurality of drift portions of a first conductivity typealternating with compensation regions of a second conductivity type, thedrift portions comprising a first maximum doping concentration and beingin Ohmic contact with the drain metallization, the compensation regionsbeing in Ohmic contact with the source metallization, in the peripheralarea the semiconductor body further comprising: a second semiconductorregion in Ohmic contact with the drift portions and comprising a secondmaximum doping concentration of dopants of the first conductivity type,the second maximum doping concentration being lower than the firstmaximum doping concentration of the drift portions by a factor of atleast five; and a first edge termination region of the secondconductivity type in Ohmic contact with the source metallization andadjoining the second semiconductor region, wherein the first edgetermination region comprises a first portion and a second portion thathas a lower integrated doping concentration than the first portion andis arranged between the first portion and the edge.